Virus is a particle made of nucleic acid and protein, which is infectious and able to reproduce only from inside the host cell. The word virus is derived from the latin word virion a matured virus. They are found in different shapes and sizes. The branch of biology that deals about virus is called “Virology”. As they show common characters of living and non-living beings, they are called a connecting link between living and non-living beings. The size of virus varies in between 25 nm to 250 nm in diameter. Therefore, virus is an ultra microscopic, potentially pathogenic higher nucleon protein entity that can service in a particular living host cells. They are host specific that is animal viruses do not attack plants and bacteria cells. Similarly plant viruses do not attack animal and bacteria cells. Viruses cause different types of diseases in human beings and in other organisms. They can be classified a follows
i. On the basis of type of nucleic acid present in them:
a. DNA virus (eg. small pox virus)
b. RNA virus (eg. Rhino virus, Retro virus, Polio virus)
ii. On the basis of host they attack on:
a. Animal virus (eg. Rhino virus, Retro virus, small pox virus)
b. Bacteriophase (The virus that attacks bacteria cell)
Viruses were discovered by a Russian botanist Ivonovsky in 1892 AD from tobacco plants leaves. Later Martinus Beijerinck named it virus. Viruses are so small that they can pass through the fine pores of filter paper.
Characteristics of Virus
1. They do not have cytoplasm and plasma membranes.
2. They do not have protein synthesizing machinery.
3. They do not respire.
Advantages of virus
The main advantages of virus are mentioned below.
1. As they are acellular, their body can be used for the study of fundamental cells.
2. By using viruses, vaccines can be manufactured.
3. We can extract vitamins like Biotin, Riboflavin from virus.
Disadvantage of virus
1. They cause different types of diseases in our body (Common cold, Rabies, Polio, AIDS, Mumps, Dengue, Measles, etc.)
Modes of transmission of viruses
1. They transmit through food, air and water.
2. They transmit through sex fluid.
3. They transmit from mothers to their babies.
Control measures of viruses
1. Unsafe sex and infected blood should be avoided.
2. Proper vaccination and immunization.
3. Infected plants and their parts should be burnt or burried deeply under the earth.
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